\documentclass{article}

\usepackage{pgfplots}

\pgfplotsset{compat=1.15}

% \usetikzlibrary{}
\usepgfplotslibrary{fillbetween}

\begin{document}



\begin{tikzpicture}
  \begin{axis}[
  ]
    \addplot[name path = ff,trig format plots=rad] ({cos(x)},x);%
    \addplot[name path = y,red] (0,x);

    \addplot fill between[of=ff and y,reverse=true,soft clip={domain y=-2:4}];
  \end{axis}
\end{tikzpicture}

\end{document}

